1. Field of the Invention
The invention relates to an improved magnetic head structure which allows the reading of recorded data, from a magnetic recording media, without picking up spurious signals. More specifically, the invention allows the reading of servo information without suffering servo errors.
2. Prior Art
The use of magnetic heads for recording and reproducing information on a recording media is well known and has become more important in recent years. Although the magnetic recording media may take a plurality of different forms, e.g. disc (flexible and/or solid) tape, etc., there are only few characteristics which are necessary to identify such medias. Generally, a slurry in which magnetic particles are suspended is uniformly spread over a thin supporting structure. The structure is then cured to form a recording media.
When a magnetic field, which is created by a magnetic head, etc., is passed relative to the surface of the recording media, the magnetization of the magnetic particles are aligned in accordance with the applied magnetic field to store data. In order to recover or reproduce the stored data, a magnetic head is positioned relative to the media and by cutting the magnetic lines the recorded data is reproduced.
In order to store and/or retrieve the magnetic data, in an orderly manner, the magnetic media is generally divided into data zones and servo zones. The data zones are the areas in which data is recorded, while the servo zones are the areas in which track following servo information is recorded.
For reproducing the recorded signal the magnetic head is passed relative to the media so as to traverse both data and servo zones. One problem associated with this system is that as the magnetic head traverses the media, spurious readback signals are generated. The spurious readback signals are outputted with the signal envelope which contains the useful data to be recovered. These spurious signals hereinafter called minor bit, present problems for the detection circuits which process the reproduced signals. In fact, whenever the problem occurs in the servo zone, whole data cartridges are sometimes rejected as being defective when, in fact, these data cartridges are good.
The source of the minor bit problem is that in addition to the head gap which does normal reading, the edges of the head core and/or a nonactivated gap in a dual or multiple gap head also reads and outputs signals. Several approaches have been practiced in the prior art to solve the minor bit problem. For example, in one attempt the prior art uses filters to filter out the unwanted signal from the reproduced signal. Although this method works satisfactorily, it tends to increase system cost since the readback circuits are more complex than if the filtering function was not necessary. Also, in the situation where the minor bit is mainly associated with the servo zone of the recording media, the filtering circuit has minimal use since the filtering circuit is only operable for the relatively short period of time when the magnetic head is traversing the servo zone.
In still another attempt the prior art uses shielding to solve the minor bit problem. However, shielding tends to increase head cost and also the complexity of the head. Also, shielding does not solve the minor bit problem in all cases, for example, when the nonactive gap of a dual gap head is reading servo data as the head tranverses the servo zone.